FEAT add scikit-learn wrappers (#20599)

* FEAT add scikit-learn wrappers

* import cleanup

* run black

* linters

* lint

* add scikit-learn to requirements-common

* generate public api

* fix tests for sklearn 1.5

* check fixes

* skip numpy tests

* xfail instead of skip

* apply review comments

* change names to SKL* and add transformer example

* fix API and imports

* fix for new sklearn

* sklearn1.6 test

* review comments and remove random_state

* add another skipped test

* rename file

* change imports

* unindent

* docstrings

keras/__init__.py

@@ -49,6 +49,7 @@
 from keras.api import utils
 from keras.api import version
 from keras.api import visualization
+from keras.api import wrappers
 
 # END DO NOT EDIT.
 

keras/api/__init__.py

@@ -32,6 +32,7 @@
 from keras.api import tree
 from keras.api import utils
 from keras.api import visualization
+from keras.api import wrappers
 from keras.src.backend import Variable
 from keras.src.backend import device
 from keras.src.backend import name_scope

keras/api/_tf_keras/keras/__init__.py

@@ -25,6 +25,7 @@
 from keras.api import tree
 from keras.api import utils
 from keras.api import visualization
+from keras.api import wrappers
 from keras.api._tf_keras.keras import backend
 from keras.api._tf_keras.keras import layers
 from keras.api._tf_keras.keras import losses

keras/api/_tf_keras/keras/wrappers/__init__.py

@@ -0,0 +1,9 @@
+"""DO NOT EDIT.
+
+This file was autogenerated. Do not edit it by hand,
+since your modifications would be overwritten.
+"""
+
+from keras.src.wrappers.sklearn_wrapper import SKLearnClassifier
+from keras.src.wrappers.sklearn_wrapper import SKLearnRegressor
+from keras.src.wrappers.sklearn_wrapper import SKLearnTransformer

keras/api/wrappers/__init__.py

@@ -0,0 +1,9 @@
+"""DO NOT EDIT.
+
+This file was autogenerated. Do not edit it by hand,
+since your modifications would be overwritten.
+"""
+
+from keras.src.wrappers.sklearn_wrapper import SKLearnClassifier
+from keras.src.wrappers.sklearn_wrapper import SKLearnRegressor
+from keras.src.wrappers.sklearn_wrapper import SKLearnTransformer

keras/src/wrappers/__init__.py

@@ -0,0 +1,5 @@
+from keras.src.wrappers.sklearn_wrapper import SKLearnClassifier
+from keras.src.wrappers.sklearn_wrapper import SKLearnRegressor
+from keras.src.wrappers.sklearn_wrapper import SKLearnTransformer
+
+__all__ = ["SKLearnClassifier", "SKLearnRegressor", "SKLearnTransformer"]

keras/src/wrappers/fixes.py

@@ -0,0 +1,119 @@
+import sklearn
+from packaging.version import parse as parse_version
+from sklearn import get_config
+
+sklearn_version = parse_version(parse_version(sklearn.__version__).base_version)
+
+if sklearn_version < parse_version("1.6"):
+
+    def patched_more_tags(estimator, expected_failed_checks):
+        import copy
+
+        from sklearn.utils._tags import _safe_tags
+
+        original_tags = copy.deepcopy(_safe_tags(estimator))
+
+        def patched_more_tags(self):
+            original_tags.update({"_xfail_checks": expected_failed_checks})
+            return original_tags
+
+        estimator.__class__._more_tags = patched_more_tags
+        return estimator
+
+    def parametrize_with_checks(
+        estimators,
+        *,
+        legacy: bool = True,
+        expected_failed_checks=None,
+    ):
+        # legacy is not supported and ignored
+        from sklearn.utils.estimator_checks import parametrize_with_checks  # noqa: F401, I001
+
+        estimators = [
+            patched_more_tags(estimator, expected_failed_checks(estimator))
+            for estimator in estimators
+        ]
+
+        return parametrize_with_checks(estimators)
+else:
+    from sklearn.utils.estimator_checks import parametrize_with_checks  # noqa: F401, I001
+
+
+def _validate_data(estimator, *args, **kwargs):
+    """Validate the input data.
+
+    wrapper for sklearn.utils.validation.validate_data or
+    BaseEstimator._validate_data depending on the scikit-learn version.
+
+    TODO: remove when minimum scikit-learn version is 1.6
+    """
+    try:
+        # scikit-learn >= 1.6
+        from sklearn.utils.validation import validate_data
+
+        return validate_data(estimator, *args, **kwargs)
+    except ImportError:
+        return estimator._validate_data(*args, **kwargs)
+    except:
+        raise
+
+
+def type_of_target(y, input_name="", *, raise_unknown=False):
+    # fix for raise_unknown which is introduced in scikit-learn 1.6
+    from sklearn.utils.multiclass import type_of_target
+
+    def _raise_or_return(target_type):
+        """Depending on the value of raise_unknown, either raise an error or
+        return 'unknown'.
+        """
+        if raise_unknown and target_type == "unknown":
+            input = input_name if input_name else "data"
+            raise ValueError(f"Unknown label type for {input}: {y!r}")
+        else:
+            return target_type
+
+    target_type = type_of_target(y, input_name=input_name)
+    return _raise_or_return(target_type)
+
+
+def _routing_enabled():
+    """Return whether metadata routing is enabled.
+
+    Returns:
+        enabled : bool
+            Whether metadata routing is enabled. If the config is not set, it
+            defaults to False.
+
+    TODO: remove when the config key is no longer available in scikit-learn
+    """
+    return get_config().get("enable_metadata_routing", False)
+
+
+def _raise_for_params(params, owner, method):
+    """Raise an error if metadata routing is not enabled and params are passed.
+
+    Parameters:
+        params : dict
+            The metadata passed to a method.
+        owner : object
+            The object to which the method belongs.
+        method : str
+            The name of the method, e.g. "fit".
+
+    Raises:
+        ValueError
+            If metadata routing is not enabled and params are passed.
+    """
+    caller = (
+        f"{owner.__class__.__name__}.{method}"
+        if method
+        else owner.__class__.__name__
+    )
+    if not _routing_enabled() and params:
+        raise ValueError(
+            f"Passing extra keyword arguments to {caller} is only supported if"
+            " enable_metadata_routing=True, which you can set using"
+            " `sklearn.set_config`. See the User Guide"
+            " <https://scikit-learn.org/stable/metadata_routing.html> for more"
+            f" details. Extra parameters passed are: {set(params)}"
+        )

keras/src/wrappers/sklearn_test.py

@@ -0,0 +1,119 @@
+"""Tests using Scikit-Learn's bundled estimator_checks."""
+
+from contextlib import contextmanager
+
+import pytest
+
+import keras
+from keras.src.backend import floatx
+from keras.src.backend import set_floatx
+from keras.src.layers import Dense
+from keras.src.layers import Input
+from keras.src.models import Model
+from keras.src.wrappers import SKLearnClassifier
+from keras.src.wrappers import SKLearnRegressor
+from keras.src.wrappers import SKLearnTransformer
+from keras.src.wrappers.fixes import parametrize_with_checks
+
+
+def dynamic_model(X, y, loss, layers=[10]):
+    """Creates a basic MLP classifier dynamically choosing binary/multiclass
+    classification loss and ouput activations.
+    """
+    n_features_in = X.shape[1]
+    inp = Input(shape=(n_features_in,))
+
+    hidden = inp
+    for layer_size in layers:
+        hidden = Dense(layer_size, activation="relu")(hidden)
+
+    n_outputs = y.shape[1] if len(y.shape) > 1 else 1
+    out = [Dense(n_outputs, activation="softmax")(hidden)]
+    model = Model(inp, out)
+    model.compile(loss=loss, optimizer="rmsprop")
+
+    return model
+
+
+@contextmanager
+def use_floatx(x: str):
+    """Context manager to temporarily
+    set the keras backend precision.
+    """
+    _floatx = floatx()
+    set_floatx(x)
+    try:
+        yield
+    finally:
+        set_floatx(_floatx)
+
+
+EXPECTED_FAILED_CHECKS = {
+    "SKLearnClassifier": {
+        "check_classifiers_regression_target": "not an issue in sklearn>=1.6",
+        "check_parameters_default_constructible": (
+            "not an issue in sklearn>=1.6"
+        ),
+        "check_classifiers_one_label_sample_weights": (
+            "0 sample weight is not ignored"
+        ),
+        "check_classifiers_classes": (
+            "with small test cases the estimator returns not all classes "
+            "sometimes"
+        ),
+        "check_classifier_data_not_an_array": (
+            "This test assumes reproducibility in fit."
+        ),
+        "check_supervised_y_2d": "This test assumes reproducibility in fit.",
+        "check_fit_idempotent": "This test assumes reproducibility in fit.",
+    },
+    "SKLearnRegressor": {
+        "check_parameters_default_constructible": (
+            "not an issue in sklearn>=1.6"
+        ),
+    },
+    "SKLearnTransformer": {
+        "check_parameters_default_constructible": (
+            "not an issue in sklearn>=1.6"
+        ),
+    },
+}
+
+
+@parametrize_with_checks(
+    estimators=[
+        SKLearnClassifier(
+            model=dynamic_model,
+            model_kwargs={
+                "loss": "categorical_crossentropy",
+                "layers": [20, 20, 20],
+            },
+            fit_kwargs={"epochs": 5},
+        ),
+        SKLearnRegressor(
+            model=dynamic_model,
+            model_kwargs={"loss": "mse"},
+        ),
+        SKLearnTransformer(
+            model=dynamic_model,
+            model_kwargs={"loss": "mse"},
+        ),
+    ],
+    expected_failed_checks=lambda estimator: EXPECTED_FAILED_CHECKS[
+        type(estimator).__name__
+    ],
+)
+def test_sklearn_estimator_checks(estimator, check):
+    """Checks that can be passed with sklearn's default tolerances
+    and in a single epoch.
+    """
+    try:
+        check(estimator)
+    except Exception as exc:
+        if keras.config.backend() == "numpy" and (
+            isinstance(exc, NotImplementedError)
+            or "NotImplementedError" in str(exc)
+        ):
+            pytest.xfail("Backend not implemented")
+        else:
+            raise